Ventriculo-Arterial Coupling and Intra-Dialytic Changes in Hemodialysis Patients: Prognostic Insights

The acute effect of hemodialysis (HD) on left ventricular mechanics has been evaluated in several studies, however their results are not uniform. Eventually, the heart and the arterial system behave as an interconnected system and not as isolated structures; thus, the evaluation of the interaction of cardiac contractility with the arterial system would provide a more comprehensive understanding of the cardiovascular function and cardiac energetics. However, there have not been any studies demonstrating changes in terms of volumes, contractility, intraventricular pressure gradients distribution, and vascular properties in response to changes in loading conditions and their impact on the outcome.

With these concepts in mind, we aim to evaluate the effect of volume changes induced by HD on ventriculo-arterial coupling (VAC) computed from speckle-tracking echocardiography. In particular, we seek to study patients with end-stage renal disease (ESRD) to assess:

1. VAC parameters before and after the hemodialysis session; 2. The value of VAC parameters in predicting adverse outcome

Three-hundred-eighty-four patients with ESRD will be evaluated by standard 2-D echocardiography before and after the HD session. Echocardiographic speckle tracking images will be analysed off-line using a dedicated software based on a mathematical model (QStrain, Medis BV, Leiden, NL). The software reconstructs the pressure/volume (PV) loop by determining the end-systolic and end-diastolic pressure-volume relationship using the single-beat algorithms. The PV relation will be depicted for the entire cardiac cycle where each point of the curve is described as (Vt, Pt). Based on this integrated PV loop analysis, the following hemodynamic parameters will be calculated: LV systolic elastance (Ees); Arterial elastance (Ea); Ventricular-Arterial Coupling (VAC); Stroke Work (SW); Pressure-volume area (PVA); Work efficiency (WE).

Patients will be followed-up for 18 months. Primary end-point will be a composite of all-cause of death, nonfatal myocardial infarction, and hospitalization due to worsening heart failure. Secondary end-point will be a composite of cardiac death, nonfatal myocardial infarction, and hospitalization for heart failure. Event-free survival for each of the echocardiographic and VAC parameters will be assessed using Kaplan-Meier analysis and compared with a log-rank test, where each index will be dichotomized according to the median of its distribution. The prognostic value will be determined using the Cox proportional hazards model. Differences will be considered statistically significant when p \<0.05.